Hey folks! This one has me stumped big time. It's a 20hp kohler model MV20s, apposed twin. Here's what's happening. While the engine is running the throttle butterfly gets very hard to turn. While the engine is off the butterfly turns freely. This is with the governor linkage disconected. You can literally run the engine without the linkage and the throttle butterfly will stay locked in place. I've went as far as replaceing the carb with a new one and have the exact same results. This happens weather the engine is cold or warm.